Numerical Feasibility Study of Self-Regulating Radiant Ceiling in Combination with Diffuse Ceiling Ventilation

A focus on indoor comfort and tightening targets for energy savings in buildings presents new opportunities for heating, ventilation, and air-conditioning products (HVAC). This paper presents a novel comfort solution that integrates a suspended radiant ceiling with diffuse ventilation, dubbed HVACeiling. In combination with the concrete slab, the HVACeiling has the potential to provide thermal comfort with minimal temperature offset, which supports operation of the heating and cooling system at temperatures very close to the room comfort temperature. The paper presents a parametric numerical study of the concept in a simplified two-pipe layout with fixed flow and fixed temperatures. First, the analysis was focused on different internal and solar loads, heat losses, and climatic locations with the aim of assessing the potential of self-regulation, i.e., no active controls, thermal comfort, ability to reduce peak loads and the consequential building design considerations. Secondly, the purpose was to analyse the concept in a generic office building with five offices and one meeting room and compare it to other HVAC solutions. The whole-year analyses of heating, cooling, energy performance, and thermal comfort were done using the building performance simulation software IDA ICE. It was found that it was possible to create thermal comfort in Paris, Munich, and Copenhagen with water circulating constantly with fixed temperatures of 20–24 °C without controls and with window sizes from 15 to 30% of the floor area. The studies showed that the HVACeiling reduced the operative peak temperatures on the warmest days in comparison with a standard radiant ceiling with mixing ventilation by 1 K. Compared to all-air solutions, the HVACeiling reduced the yearly energy consumption by 20–30% and the peak power in summer up to 69%. This study indicates that thermal comfort is achievable in a European context even at very small temperature offsets, which supports the use of more renewable energy sources.